The present invention relates to a data storage device, and more specifically to a buffer control method in a data storage device.
Data storage devices using various types of media such as optical disks, magnetic tapes and semiconductor memories are known in the art. Among them, hard disk drives (hereinafter referred to as HDDs) have become popular as storage devices for computers to such an extent that they are one type of the storage devices indispensable for today's computers. Further, not limited to computer systems, HDDs are expanding more and more in application because of its excellent characteristics. For example, HDDs are used for moving picture recording/reproducing devices, car navigation systems, cellular phones, and removable memories for use in digital cameras.
Each magnetic disk used in HDDs has a plurality of tracks formed concentrically and each track is partitioned into a plurality of sectors. Sector address information and user data are stored in each sector. Either data write to a sector or data read from the sector is enabled by a magnetic head which accesses the desired sector according to the sector address information. In a data read operation, a signal read out by the head from a magnetic disk is subjected to waveform shaping, decoding processing and other prescribed signal processing by a signal processing circuit before being transmitted to the host. Likewise, data transferred from the host is subjected to prescribed signal processing by the signal processing circuit and then written to the magnetic disk.
Read data that is read from the magnetic disk is temporarily stored in a buffer before being transmitted to the host. In the buffer, data that was read from the magnetic disk in the past is stored, and when data required from the host is cached in the buffer, the data stored in the buffer is transmitted to the host without making an access to the magnetic disk. With such arrangement, it is possible to improve performance of the HDD.
Several methods related to buffer control of read data have been known for improving the HDD performance. One of the methods is disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2003-122631), wherein an HDD includes a data buffer comprising a main memory and an auxiliary memory to store read or written data. At the time of initialization, data of a specified sector such as an alternating process accompanying a seek operation will be read into the auxiliary memory in advance. With such arrangement, HDD performance can be improved.